85d7809e0c
The value from raw_read_cntfrq_el0() could be large enough to cause overflow when multiplied by USECS_PER_SEC. To prevent this, both USECS_PER_SEC and tfreq can be reduced by dividing them by their GCD. BUG=b:307790895 TEST=emerge-geralt coreboot TEST=boot to kernel and check the timestamps from `cbmem` Change-Id: I366667de05392913150414f0fa9058725be71c52 Signed-off-by: Yidi Lin <yidilin@chromium.org> Reviewed-on: https://review.coreboot.org/c/coreboot/+/78800 Reviewed-by: Yu-Ping Wu <yupingso@google.com> Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
30 lines
705 B
C
30 lines
705 B
C
/* SPDX-License-Identifier: GPL-2.0-only */
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#include <arch/lib_helpers.h>
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#include <commonlib/bsd/gcd.h>
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#include <timer.h>
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void timer_monotonic_get(struct mono_time *mt)
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{
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uint64_t tvalue = raw_read_cntpct_el0();
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static uint32_t tfreq, mult;
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uint32_t div;
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/*
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* The value from raw_read_cntfrq_el0() could be large enough to
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* cause overflow when multiplied by USECS_PER_SEC. To prevent this,
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* both USECS_PER_SEC. and tfreq can be reduced by dividing them by
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* their GCD.
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*/
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if (tfreq == 0) {
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tfreq = raw_read_cntfrq_el0();
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mult = USECS_PER_SEC;
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div = gcd32(tfreq, mult);
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tfreq /= div;
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mult /= div;
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}
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long usecs = (tvalue * mult) / tfreq;
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mono_time_set_usecs(mt, usecs);
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}
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